A Wireless Low-Power Single-Unit Wearable System for Continuous Early Warning Score Calculation

In this work, we present a new device to monitor the five main vital parameters of hospitalized patients: heart rate (HR), respiratory rate (RR), blood oxygen saturation, blood pressure (BP), and temperature. The device consists of one single unit placed on the chest with two electrodes connected to the patient. The device continuously acquires the electrocardiogram (ECG), three-wavelength photoplethysmogram (PPG), bioimpedance, body temperature, and three-axis acceleration. These raw data are securely sent via a Wi-Fi access point to a local server where algorithms are running to calculate the five vital parameters, combined with the level of activity and the posture. Alarms, live stream, and a real-time estimation of the early warning score (EWS) used to assess the instantaneous state of a patient are available to nurses to react quickly and adequately if needed. Due to its small form factor and weight, the device is worn unobtrusively by the patient who can move without being restrained by wires; a small battery ensures an autonomy of a few days. In this article, the firmware and hardware architectures are detailed comprising the list of the sensors, the main chips used, and the casing. The relationships between what the sensors measure and the vital parameters of interest are discussed.